The scientific journal that published Facebook’s controversial social experiment has issued a statement expressing “concern” over the lack of informed consent from Facebook users who unknowingly participated.

The study by researchers from Facebook and Cornell University sparked outrage this week after word spread that the Facebook feeds of nearly 700,000 users had been secretly manipulated to study the social network’s emotional impact. The researchers claimed the Facebook users consented to the study by, well, being Facebook users.

According to statements from the journal and Cornell, Facebook did not need the type of informed consent typically required for studies because it’s a private company and is therefore held to different standards than universities and scientific journals.

“It is nevertheless a matter of concern that the collection of the data by Facebook may have involved practices that were not fully consistent with the principles of obtaining informed consent and allowing participants to opt out,” the journal’s editor-in-chief, Inder Verma, said in the statement.

According to the study footnote, researchers from Cornell joined a researcher from Facebook to design the study, but sat out the controversial step of collecting and analyzing data from Facebook users. They then returned to write the paper.

“As such, it was consistent with Facebook’s Data Use Policy, to which all users agree prior to creating an account on Facebook, constituting informed consent for this research,” read the study.

This is where the “ethical conundrum” begins, said bioethicist and lawyer Leslie Meltzer Henry, who works at the Johns Hopkins Berman Institute of Bioethics and the University of Maryland Carey School of Law.

“The type of one-click consent that Facebook users provide when they agree to the site’s data use policy is very different from the type of informed consent that’s ethically and legally required” of most biomedical or behavioral studies, said Meltzer Henry, adding that one-click-consent “is inadequate to cover the potential harm” that can come from participation in a study that involves emotional manipulation.